[Cup Placement in Thumb Carpometacarpal Joint Prostheses: The Role of the Guidewire]. / Pfannenplatzierung bei Daumensattelgelenksprothesen: Die Rolle des Führungsdrahts.

BACKGROUND: The increasing use of thumb carpometacarpal joint prostheses for advanced CMC 1 (carpometacarpal) joint arthritis reflects the success of the latest prosthesis generations, which has been achieved through their improved functional outcomes and lower complication rates. Precise alignment of the prosthesis cup parallel to the proximal joint surface of the trapezium is essential for stability and the prevention of dislocation. This is a challenging surgical step, particularly for surgeons new to this technique. Despite adequate positioning of the guidewire, misplacements of the cup may occur, necessitating intraoperative revision. MATERIAL AND METHODS: This study examined the deviations in cup and guidewire positioning in thumb carpometacarpal joint prosthesis implantations by inexperienced and experienced surgeons through radiological analysis of 65 prostheses. RESULTS: Both inexperienced and experienced surgeons achieved precise guidewire positioning with mean deviations of<2.2°. Inexperienced surgeons showed significantly larger cup deviations in the dorsopalmar and lateral view (7.6±6.1° and 7.3±5.9°) compared with experienced surgeons (3.6±2.7° and 3.6±2.5°; p=0.012, p=0.017). The deviation of the cup position exhibited by inexperienced surgeons tends to be in the direction opposite to the initial guidewire position (p<0.0038). CONCLUSION: The results highlight the current challenges in cup positioning depending on a surgeon's level of experience, questioning the reliability of the current guidewire placement.

Computer-simulated TOUCH prosthesis cup malposition and solutions.

INTRODUCTION: Total joint replacement has become significantly more common as a treatment for advanced trapeziometacarpal joint osteoarthritis in recent years. The latest generation of prostheses with dual-mobility designs leads to very good functional results and low rates of loosening and dislocation in the short and medium term. Biomechanical studies showed that central placement and parallel alignment of the cup with respect to the proximal articular surface of the trapezium are crucial for both cup stability and prevention of dislocation. Despite correct positioning of the guidewire, incorrect placement or tilting of the inserted cup may occur, requiring immediate intraoperative revision. METHODS: The existing spherical and conical cup models in sizes 9 mm and 10 mm were transferred to a computer-aided design dataset. Depending on the intraoperative complication (tilting or incorrect placement), the revision options resulting from the various combinations of cup type and size were simulated and analyzed according to the resulting defect area and bony contact area. RESULTS: In well centered cups, a size 9 conical cup could be replaced by a size 9 spherical cup and still be fixed by press-fit. Conversely, a size 9 spherical cup could not be replaced by a size 9 conical cup, but only by a size 10 cup, of whatever shape. When a size 9 conical cup was tilted up to 20°, the best revision option was to resect the sclerotic margin and insert a size 10 conical cup deeper into the cancellous bone, to achieve the largest contact area with the surrounding bone. When a size 9 cup of whatever shape was poorly centered (misplaced with respect to the dorsopalmar or radioulnar line of the trapezium), placement should be corrected using a size 10 cup, combined with autologous bone grafting of the defect. Again, the size 10 conical cup showed the largest bony contact area. CONCLUSION: Our computer-based measurements suggested options for intraoperative cup revision depending on cup shape and size and on type of misalignment with resulting bone defects. These suggestions, however, need to be confirmed in anatomic specimens before introducing them into clinical practice.

Is taper corrosion in modular revision hip stem junctions associated with patient or implant specific factors? A retrieval analysis.

Implant modularity within revision total hip arthroplasty (THA) offers multiple implant configurations and allows surgeons a high intraoperative flexibility to restore functionality to the patients joint, even in complex revision cases. However, a rare but devastating complication for patients, clinicians and manufacturers presenting a breakage of the taper junction between the distal stem and the proximal implant part. Aside from implant and patient specific risk factors, corrosion and fretting at the stem junctions have been associated with taper failure. Whether corrosive processes are a precursor of failure or rather an accompaniment of material fatigue is thereby still unclear. Therefore, this study aims to investigate the incidence of taper corrosion in a collection of 17 retrievals from a single type (MRP-Titan, Peter Brehm GmbH) and on the correlation of taper corrosion to implant and patient specific factors. None of the implants was revised for problems related to the taper junction, corrosion or the implant itself. The modular stem junction of all retrievals was visually rated with respect to corrosion, fretting and surface contamination. Additionally, the stability of taper junctions of retrievals where the proximal part with the neck was still assembled to the stem was determined by measuring the loosening moment of the securing screw and the push-out-force for taper dissociation. There was no difference between the mean push-out-force of the retrievals (14 kN ± 1.2 kN) and new reference samples (12.6 kN ± 0.5 kN). Approximately one third of the investigated retrievals showed considerable taper corrosion. The extent of corrosion increased with time in vivo and contamination of the neck piece, while it decreased with the loosening moment of the locking screw. The parameters femoral head offset, neck piece length, lateralized neck pieces, obesity of patients and septic/aseptic revision were not correlated to taper corrosion. Taper corrosion seems to occur regularly in modular taper junctions and is not necessarily connected to taper failure. A correct assembly of the junction and avoiding taper surface contamination during revision surgery is mandatory.

Reply to Alt et al. Comment on "Lunz et al. Impact and Modification of the New PJI-TNM Classification for Periprosthetic Joint Infections. J. Clin. Med. 2023, 12, 1262".

We greatly appreciate the comments made by Alt et al. [...].

Enhanced antibiotic release from bone cement spacers utilizing dual antibiotic loading with elevated vancomycin concentrations in two-stage revision for periprosthetic joint infection.

PURPOSE: Antibiotic loaded bone cement spacers provide high local antibiotic concentrations, preserve bone stock, and reduce soft tissue contractions. The objective of this in-vitro study was to compare antibiotic release from spacers, aiming to discover the most optimal preparation and identify modifiable factors that can further enhance antibiotic release. METHODS: Six distinct spacer preparation were created using three different bone cements and manual incorporation of antibiotics. During a six-week period, the release of antibiotics from each spacer was measured individually at ten predetermined time points using a chemiluminescent immunoassay. RESULTS: Manually adding 4 g of vancomycin to every 40 g of "Palacos R + G" yielded the most favorable release profile. Throughout all preparations, antibiotic release consistently and significantly decreased over the six-week period. When incorporating a higher concentration of vancomycin, a significantly higher cumulative release of vancomycin was observed, with varying effects on the release of gentamicin. The choice of bone cement had a significant impact on antibiotic release. CONCLUSION: To enhance antibiotic release from spacers, surgeons should manually incorporate high antibiotic concentrations into the most appropriate bone cement and keep the interim period as short as possible. Specifically, we suggest manual incorporation of 4 g of vancomycin to every 40 g of gentamicin premixed "Palacos R + G" to create bone cement spacers.

Minimum 20-year follow-up of a press-fit acetabular cup in cementless total hip replacement in young patients.

PURPOSE: We aimed to determine the minimum 20-year survival rates of a cementless press-fit cup in young patients. PATIENTS AND METHODS: This is a retrospective, single-center, multi-surgeon cohort study investigating the minimum 20-year clinical and radiological outcome of the first 121 consecutive total hip replacements (THRs) using a cementless, press-fit cup (Allofit, Zimmer, Warsaw, IN, USA) performed between 1999 and 2001. 28-mm metal-on-metal (MoM) and ceramic-on-conventionally not highly crosslinked polyethylene (CoP) bearings were used in 71% and 28%, respectively. Median patient age at surgery was 52 (range 21-60) years. Kaplan-Meier survival analysis was conducted for different endpoints. RESULTS: The 22-year survival rate for the endpoint aseptic cup or inlay revision was 94% (95% confidence interval [CI] 87-96) and 99% (CI 94-100) for aseptic cup loosening. 20 patients (21 THRs; 17%) had died and 5 (5 THRs; 4%) were lost to follow-up. No THR showed evidence of radiographic cup loosening. Osteolysis was observed in 40% of THRs with MoM and 77% with CoP bearings. 88% of THRs with CoP bearings showed significant polyethylene wear. CONCLUSION: The investigated cementless press-fit cup, which is still in clinical use today, showed excellent long-term survival rates in patients under the age of 60 years at surgery. However, osteolysis due to polyethylene and metal wear was frequently observed and is a matter of concern in the third decade after surgery.

Stability of ceramic coatings on retrieved knee prostheses.

BACKGROUND: In total knee arthroplasty, femoral components with coated or oxidized surfaces are commonly used as alternative to CoCrMo in metal sensitive patients. Data on the in vivo behaviour of different coating types is, however, rare. Aim of the study was the investigation of coating stability with respect to implant and patient specific parameters. METHODS: Coating thickness and coating thickness reduction, respectively, was measured at 37 retrieved femoral components with TiNbN, TiN, ZrN or oxidized zirconium (OxZr) surface by the crater grinding method. The results were correlated to surface type, manufacturer, time in vivo of the implant, patient body weight and patient activity. RESULTS: Mean coating thickness reduction in the overall retrieval collection was 0.6 µm ± 0.8 µm. There was no correlation between coating thickness reduction and coating type, time in vivo, patient body weight, and patient activity. If grouped according to manufacturers, implants of one manufacturer showed an increased coating thickness reduction. 10 of 37 retrievals exhibited coating abrasion with exposure of the underlying alloy. TiNbN coatings showed the highest incidence (9/17) of coating abrasion. No coating breakthrough was observed in the ZrN or OxZr surfaces. CONCLUSION: Our results indicate that TiNbN coatings should be optimized to improve their wear resistance in the long-term.

Impact and Modification of the New PJI-TNM Classification for Periprosthetic Joint Infections.

The comprehensive "PJI-TNM classification" for the description of periprosthetic joint infections (PJI) was introduced in 2020. Its structure is based on the well-known oncological TNM classification to appreciate the complexity, severity, and diversity of PJIs. The main goal of this study is to implement the new PJI-TNM classification into the clinical setting to determine its therapeutic and prognostic value and suggest modifications to further improve the classification for clinical routine use. A retrospective cohort study was conducted at our institution between 2017 and 2020. A total of 80 consecutive patients treated with a two-stage revision for periprosthetic knee joint infection were included. We retrospectively assessed correlations between patients' preoperative PJI-TNM classification and their therapy and outcome and identified several statistically significant correlations for both classifications, the original and our modified version. We have demonstrated that both classifications provide reliable predictions already at the time of diagnosis regarding the invasiveness of surgery (duration of surgery, blood and bone loss during surgery), likelihood of reimplantation, and patient mortality during the first 12 months after diagnosis. Orthopedic surgeons can use the classification system preoperatively as an objective and comprehensive tool for therapeutic decisions and patient information (informed consent). In the future, comparisons between different treatment options for truly similar preoperative baseline situations can be obtained for the first time. Clinicians and researchers should be familiar with the new PJI-TNM classification and start implementing it into their routine practice. Our adjusted and simplified version ("PJI-pTNM") might be a more convenient alternative for the clinical setting.

Is TKA femoral implant stability improved by pressure applied cement? a comparison of 2 cementing techniques.

BACKGROUND: The majority of knee endoprostheses are cemented. In an earlier study the effects of different cementing techniques on cement penetration were evaluated using a Sawbone model. In this study we used a human cadaver model to study the effect of different cementing techniques on relative motion between the implant and the femoral shaft component under dynamic loading. METHODS: Two different cementing techniques were tested in a group of 15 pairs of human fresh frozen legs. In one group a conventional cementation technique was used and, in another group, cementation was done using a pressurizing technique. Under dynamic loading that simulated real life conditions relative motion at the bone-implant interface were studied at 20 degrees and 50 degrees flexion. RESULTS: In both scenarios, the relative motion anterior was significantly increased by pressure application. Distally, it was the same with higher loads. No significant difference could be measured posteriorly at 20°. At 50° flexion, however, pressurization reduced the posterior relative motion significantly at each load level. CONCLUSION: The use of the pressurizer does not improve the overall fixation compared to an adequate manual cement application. The change depends on the loading, flexion angle and varies in its proportion in between the interface zones.

Pulsatile Lavage Improves Tibial Cement Penetration and Implant Stability in Medial Unicompartmental Arthroplasty: A Cadaveric Study.

Cemented unicompartmental knee arthroplasty (UKA) shows good survivorship and function. However, implant failure, causing the need for revision, can occur. Aseptic loosening is still among the most common reasons for revision. The purpose of this study was to assess the influence of preimplantation lavage technique on tibial cement penetration depth, tibial cement volume, and load to fracture in the tibial component of mobile-bearing UKA. In 10 pairs of fresh frozen human tibiae, cemented UKA was implanted by an experienced surgeon. Tibial components were then implanted, left and right tibiae were randomly allocated to group A or B. Prior to implantation, irrigation was performed with either syringe lavage or pulsatile jet lavage in a standardized manner. Cement surface was 4170.2 mm2 (3271.6-5497.8 mm2) in the syringe lavage group, whereas the jet lavage group showed 4499.3 mm2 (3354.3-5809.1 mm2); cement volume was significantly higher as well (4143.4 mm3 (2956.6-6198.6 mm3) compared with 5936.9 mm3 (3077.5-8183.1 mm3)). Cement penetration depth was 2.5 mm (1.7-3.2 mm) for the jet lavage, and 1.8 mm (1.2-2.4 mm) for the syringe lavage. The mean fracture load was 4680 N in the jet lavage group and 3800 N in the syringe lavage group (p = 0.001). Subsidence was significantly higher for syringe lavage. This study suggests a correlation of cement penetration depth and cement volume to implant failure in the tibial component of a UKA using a cadaveric model. The type of bone lavage most likely influences these two key parameters.

Dissociation of liner from cup in THA: does liner damage affect the risk of dissociation?

INTRODUCTION: A rare catastrophic failure of modular component Total Hip Arthroplasty is dissociation between liner and cup, which has been associated with component malposition and/or impingement and seems to be more frequently associated with the Pinnacle system. The goal of this study was to evaluate the resistance of a polyethylene liner to lever-out-forces of the Pinnacle locking mechanism and the locking mechanisms of two other current cup/liner systems using a standardized testing method (ASTM). MATERIALS AND METHODS: Five of each of the following cups were evaluated with their corresponding polyethylene liners: Pinnacle Multihole cup with and without intact anti-rotation tabs (ART's); Allofit-S-Alloclassic and Plasmafit Plus7 cups. The ASTM test set-up was used to evaluate the lever-out force resulting in liner dissociation for each construct. RESULTS: The Pinnacle construct with intact ARTs required the greatest force (F) to achieve dissociation (263.2 ± 79.2 N) followed by the Plasmafit Plus7 (185.8 ± 36.9 N) and the Allofit-S (101.4 ± 35.3 N) constructs, respectively. However, after removal of the ARTs, the Pinnacle system required the least force to achieve dissociation (75.1 ± 22.2 N) (p < 0.001). CONCLUSIONS: The intact Pinnacle system appeared the most stable in lever-out tests when compared to the other systems. However, after removal of the ARTs, the Pinnacle system required the least force for dissociation, consistent with locking mechanism failure, and suggesting that the ARTs are a critical component of the locking mechanism. Our findings are consistent with the clinical experience of dissociated Pinnacle constructs displaying damaged or missing ARTs, and that damage to these may increase risk of liner dissociation.

Pulsatile lavage systems and their potential to penetrate soft tissue.

BACKGROUND: In orthopedic and trauma surgery, pulsatile lavage systems are used to clean soft tissue. This may be necessary in septic surgeries or in case of contaminated wounds after trauma. Positive features such as reduction of bacterial contamination and removal of foreign particles are counterbalanced by negative aspects such as bacterial seeding in deeper tissue layers, damage to various tissues and even cases of air embolism. PURPOSE: The aim of this prospective experimental in vitro study was to compare impact pressure and flow rate in three different pulsatile lavage systems and to determine, whether these parameters alter their ability to reach deeper soft tissue layers. METHODS: To test the penetration of soft tissue, the muscle tissue was flushed with contrast medium instead of saline fluid and afterwards scanned by computed tomography. RESULTS: Impact pressure and flow rate showed significant differences between the different systems. There were no significant differences between the three devices in terms of total penetration volume, but there were significant differences in penetration depth. CONCLUSION: In this study, we found that higher impact pressure leads to deeper penetration and therefore bacteria are likely to be transferred to deeper tissue layers.

Mechanical strength of antibiotic-loaded PMMA spacers in two-stage revision surgery.

BACKGROUND: Antibiotic-loaded polymethylmethacrylate (PMMA) bone cement spacers provide high local antibiotic concentrations and patient mobility during the interim period of two-stage revision for periprosthetic joint infection (PJI). This study compares mechanical characteristics of six dual antibiotic-loaded bone cement (dALBC) preparations made from three different PMMA bone cements. The study`s main objective was to determine the effect of time and antibiotic concentration on mechanical strength of dALBCs frequently used for spacer fabrication in the setting of two-stage revision for PJI. METHODS: A total of 84 dual antibiotic-loaded bone cement specimens made of either Copal spacem, Copal G + V or Palacos R + G were fabricated. Each specimen contained 0.5 g of gentamicin and either 2 g (low concentration) or 4 g (high concentration) of vancomycin powder per 40 g bone cement. The bending strength was determined at two different timepoints, 24 h and six weeks after spacer fabrication, using the four-point bending test. RESULTS: Preparations made from Copal G + V showed the highest bending strength after incubation for 24 h with a mean of 57.6 ± 1.2 MPa (low concentration) and 50.4 ± 4.4 MPa (high concentration). After incubation for six weeks the bending strength had decreased in all six preparations and Palacos R + G showed the highest bending strength in the high concentration group (39.4 ± 1.6 MPa). All low concentration preparations showed superior mechanical strength compared to their high concentration (4 g of vancomycin) counterpart. This difference was statistically significant for Copal spacem and Copal G + V (both p < 0.001), but not for Palacos R + G (p = 0.09). CONCLUSIONS: This study suggests that mechanical strength of antibiotic-loaded PMMA bone cement critically decreases even over the short time period of six weeks, which is the recommended interim period in the setting of two-stage revision. This potentially results in an increased risk for PMMA spacer fracture at the end of the interim period and especially in patients with prolonged interim periods. Finally, we conclude that intraoperative addition of 4 g of vancomycin powder per 40 g of gentamicin-premixed Palacos R + G (Group D) is mechanically the preparation of choice if a dual antibiotic-loaded bone cement spacer with high antibiotic concentrations and good stability is warranted. In any case the written and signed informed consent including the off-label use of custom-made antibiotic-loaded PMMA bone cement spacers must be obtained before surgery.

Accuracy measurement of different marker based motion analysis systems for biomechanical applications: A round robin study.

INTRODUCTION: Multiple camera systems are widely used for 3D-motion analysis. Due to increasing accuracies these camera systems gained interest in biomechanical research areas, where high precision measurements are desirable. In the current study different measurement systems were compared regarding their measurement accuracy. MATERIALS AND METHODS: Translational and rotational accuracy measurements as well as the zero offset measurements of seven different measurement systems were performed using two reference devices and two different evaluation algorithms. All measurements were performed in the same room with constant temperature at the same laboratory. Equal positions were measured with the systems according to a standardized protocol. Measurement errors were determined and compared. RESULTS: The highest measurement errors were seen for a measurement system using active ultrasonic markers, followed by another active marker measurement system (infrared) having measurement errors up to several hundred micrometers. The highest accuracies were achieved by three stereo camera systems, using passive 2D marker points having errors typically below 20 µm. CONCLUSIONS: This study can help to better assess the results obtained with different measurement systems. With the focus on the measurement accuracy, only one aspect in the selection of a system was considered. Depending on the requirements of the user, other factors like measurement frequency, the maximum analyzable volume, the marker type or the costs are important factors as well.

Does Kinematic Alignment Increase Polyethylene Wear Compared With Mechanically Aligned Components? A Wear Simulation Study.

BACKGROUND: Kinematic alignment is an alternative approach to mechanical alignment. Kinematic alignment can restore the joint line to its prearthritic condition, and its advocates have suggested it may be associated with other benefits. But this alignment approach often results in tibial components that are placed in varus and femoral components that are placed in valgus alignment, which may result in an increased risk of component loosening because of wear. Like malaligned implant components, kinematically aligned knee implants could increase wear in vivo, but we lack comparative data about wear behavior between these approaches. QUESTIONS/PURPOSES: (1) Do the different alignment approaches (kinematic, mechanical, and purposefully malaligned components) result in different wear rates in a wear simulator? (2) Do the different alignment approaches lead to different worn areas on the polyethylene inserts in a wear simulator? (3) Do the different alignment approaches result in different joint kinematics in a wear simulator? METHODS: Mechanical alignment was simulated in a force-controlled manner with a virtual ligament structure according to the International Organization for Standardization (ISO 14243-1) using a knee wear simulator. To simulate kinematic alignment, flexion-extension motion, internal-external torque, and the joint line were tilted by 4°, using a novel mechanical setup, without changing the force axis. The setup includes bearings with inclinations of 4° so that the joint axis of 4° is determined. To verify the angle of 4°, a digital spirit level was used. To simulate malalignment, we tilted the implant and, therefore, the joint axis by 4° using a wedge with an angle of 4° without tilting the torque axes of the simulator. This leads to a purposefully malaligned tibial varus and femoral valgus of 4°. For each condition, three cruciate-retaining knee implants were tested for 3.0 x 10 6 cycles, and one additional implant was used as soak control. Gravimetric wear analyses were performed every 0.5 x 10 6 cycles to determine the linear wear rate of each group by linear regression. The wear area was measured after 3.0 x 10 6 cycles by outlining the worn areas on the polyethylene inserts, then photographing the inserts and determining the worn areas using imaging software. The joint kinematics (AP translation and internal-external rotation) were recorded by the knee simulator software and analyzed during each of the six simulation intervals. RESULTS: Comparing the wear rates of the different groups, no difference could be found between the mechanical alignment and the kinematic alignment (3.8 ± 0.5 mg/million cycles versus 4.1 ± 0.2 mg/million cycles; p > 0.99). However, there was a lower wear rate in the malaligned group (2.7 ± 0.2 mg/million cycles) than in the other two groups (p < 0.01). When comparing the total wear areas of the polyethylene inserts among the three different alignment groups, the lowest worn area could be found for the malaligned group (716 ± 19 mm 2 ; p ≤ 0.003), but there was no difference between kinematic alignment and mechanical alignment (823 ± 19 mm 2 versus 825 ± 26 mm 2 ; p > 0.99). Comparing the AP translation, no difference was found between the mechanical alignment, the kinematic alignment, and the malalignment group (6.6 ± 0.1 mm versus 6.9 ± 0.2 mm versus 6.8 ± 0.3 mm; p = 0.06). In addition, the internal-external rotation between mechanical alignment, kinematic alignment, and malalignment also revealed no difference (9.9° ± 0.4° versus 10.2° ± 0.1° versus 10.1° ± 0.6°; p = 0.44). CONCLUSION: In the current wear simulation study, the wear rates of mechanical alignment and kinematic alignment of 4° were in a comparable range. CLINICAL RELEVANCE: The results suggest that kinematic alignment with up to 4° of component inclination may give the surgeon confidence that the reconstruction will have good wear-related performance when using a modern cruciate-retaining implant. The malaligned group had the lowest wear rate, which may be a function of the smaller worn area on the inserts compared with the other two alignment groups. This smaller articulation area between the femoral condyles and polyethylene insert could increase the risk of delamination of malaligned components over longer test durations and during high-load activities. For that reason, and because malalignment can cause nonwear-related revisions, malalignment should be avoided. Further in vitro and clinical studies must prove whether the wear simulation of different alignments can predict the wear behavior in vivo.

Does tibial design modification improve implant stability for total knee arthroplasty? An experimental cadaver study.

AIMS: One of the main causes of tibial revision surgery for total knee arthroplasty is aseptic loosening. Therefore, stable fixation between the tibial component and the cement, and between the tibial component and the bone, is essential. A factor that could influence the implant stability is the implant design, with its different variations. In an existing implant system, the tibial component was modified by adding cement pockets. The aim of this experimental in vitro study was to investigate whether additional cement pockets on the underside of the tibial component could improve implant stability. The relative motion between implant and bone, the maximum pull-out force, the tibial cement mantle, and a possible path from the bone marrow to the metal-cement interface were determined. METHODS: A tibial component with (group S: Attune S+) and without (group A: Attune) additional cement pockets was implanted in 15 fresh-frozen human leg pairs. The relative motion was determined under dynamic loading (extension-flexion 20° to 50°, load-level 1,200 to 2,100 N) with subsequent determination of the maximum pull-out force. In addition, the cement mantle was analyzed radiologically for possible defects, the tibia base cement adhesion, and preoperative bone mineral density (BMD). RESULTS: The BMD showed no statistically significant difference between both groups. Group A showed for all load levels significantly higher maximum relative motion compared to group S for 20° and 50° flexion. Group S improved the maximum failure load significantly compared to group A without additional cement pockets. Group S showed a significantly increased cement adhesion compared to group A. The cement penetration and cement mantle defect analysis showed no significant differences between both groups. CONCLUSION: From a biomechanical point of view, the additional cement pockets of the component have improved the fixation performance of the implant. Cite this article: Bone Joint Res 2022;11(4):229-238.

The primary stability of the femoral component in cemented single and twin peg Oxford unicompartmental knee arthroplasty under adverse conditions.

AIMS: The cemented Oxford unicompartmental knee arthroplasty (OUKA) features two variants: single and twin peg OUKA. The purpose of this study was to assess the stability of both variants in a worst-case scenario of bone defects and suboptimal cementation. METHODS: Single and twin pegs were implanted randomly allocated in 12 pairs of human fresh-frozen femora. We generated 5° bone defects at the posterior condyle. Relative movement was simulated using a servohydraulic pulser, and analyzed at 70°/115° knee flexion. Relative movement was surveyed at seven points of measurement on implant and bone, using an optic system. RESULTS: At the main fixation zone, the twin peg shows less relative movement at 70°/115°. At the transition zone, relative movements are smaller for the single peg for both angles. The single peg shows higher compression at 70° flexion, whereas the twin peg design shows higher compression at 115°. X-displacement is significantly higher for the single peg at 115°. CONCLUSION: Bony defects should be avoided in OUKA. The twin peg shows high resilience against push-out force and should be preferred over the single peg. Cite this article: Bone Joint Res 2022;11(2):82-90.

Does Additive Pressurized Carbon Dioxide Lavage Improve Cement Penetration and Bond Strength in Cemented Arthroplasty?

The modern cementing technique in cemented arthroplasty is a highly standardized and, therefore, safe procedure. Nevertheless, aseptic loosening is still the main reason for revision after cemented total knee or cemented total hip arthroplasty. To investigate whether an additional carbon dioxide lavage after a high-pressure pulsatile saline lavage has a positive effect on the bone-cement interface or cement penetration, we set up a standardized laboratory experiment with 28 human femoral heads. After a standardized cleaning procedure, the test implants were cemented onto the cancellous bone. Subsequently, the maximum failure load of the bone-cement interface was determined using a material testing machine to pull off the implant, and the cement penetration was determined using computed tomography. Neither the maximum failure load nor cement penetration into the cancellous bone revealed significant differences between the groups. In conclusion, according to our experiments, the additive use of the carbon dioxide lavage after the high-pressure pulsatile lavage has no additional benefit for the cleaning of the cancellous bone and, therefore, cannot be recommended without restrictions.

Cement debonding behaviors of the various tibial components of the ATTUNE knee system and its predecessors: Is a cement-in-cement revision an alternative?

BACKGROUND: Aseptic loosening remains one of the most common causes of revision of the tibial component for total knee arthroplasty. A stable bond between implant and cement is essential for appropriate long-term results. The aim of our in vitro study was to investigate the maximum failure load of tibial ATTUNE prosthesis design alternatives compared with a previous design. In addition, cement-in-cement revision was considered as a potential strategy after tibial component debonding. METHODS: The experimental investigations of the maximum failure load of the implant-cement interface were performed under optimal conditions, without potential contamination. We compared the designs of the tibial components of the ATTUNE, ATTUNE S+ and P.F.C. Sigma. In addition, we investigated the cement-in-cement revision for the ATTUNE knee system replacing it with an ATTUNE S+. RESULTS: The maximum failure load showed no significant difference between P.F.C. Sigma and ATTUNE groups (P = 0.087), but there was a significant difference between the P.F.C. Sigma and the ATTUNE S+ groups (P < 0.001). The analysis also showed a significant difference (P < 0.001) between the ATTUNE and the ATTUNE S+ groups for the maximum failure load. The ATTUNE S+ cement-in-cement revision group showed a significant higher failure load (P < 0.001) compared with the P.F.C. Sigma and ATTUNE groups. No significant differences (P = 1.000) were found between the ATTUNE S+ cement-in-cement and ATTUNE S+ group. CONCLUSION: Based on these results, we found no design-specific evidence of increased debonding risk with the ATTUNE and ATTUNE S+ components compared with the P.F.C Sigma. Furthermore, the cement-in-cement revision seems to be an alternative for the revision surgery.

Early tibial loosening of the cemented ATTUNE knee arthroplasty - Just a question of design?

BACKGROUND: Total knee arthroplasty is a very successful standard treatment for severe osteoarthritis. Nevertheless, the literature reports tibial debonding between implant and bone cement as well as radiolucent lines related to the tibial components of different knee systems. Regardless of cementing techniques and the influences during surgery, we examined the design of a newly developed knee system and its predecessors (Attune, Attune S+, P.F.C. Sigma, P.F.C. Sigma RP/M.B.T., all DePuy). METHODS: We investigated the dimensions of the tibial components and the fit between them and their bone bed after instrumentation in a foam material. RESULTS: Our results showed considerable differences for the used knee prostheses as well as their tibial instrumentation options with a corresponding risk for incomplete seating. CONCLUSION: The orthopedic surgeons need to be aware of these design features and the resulting increased seating resistance especially in hard and sclerotic bone. ARTICLE FOCUS: Comparison of the tibial instruments and the different design options of the Attune knee system and its predecessor knee prostheses. KEY MESSAGES: The Attune implant showed incomplete seating because of too much press fit and an uneven bone quality or sclerosis can result in tilting of the tibial component. STRENGTHS AND LIMITATIONS: This is the first study investigating the Attune knee and its predecessor in terms of implant seating and press fit. The foam material is a limitation.